People rally in favor of single-payer health care for all Californians outside the office of California Assembly Speaker Anthony Rendon, June 27, 2017, in South Gate, Calif., as the U.S. Senate prepares to vote on its health care bill. (Photo: Robyn Beck/AFP/Getty Images)

LOS ANGELES — Soon enough, the Republican Party’s seven-year crusade to slay the Affordable Care Act (aka Obamacare) will come to an end. On Thursday, Senate Majority Leader Mitch McConnell unveiled yet another revision of the GOP’s fraught repeal-and-replace legislation, and the controversial bill will either find the 50 Republican votes it needs to pass the upper chamber of Congress in the next few days — or it will perish once and for all.

That’s the challenge facing Republicans right now. The challenge facing Democrats is how to respond.

Going beyond attacking Republicans over a plan that would take insurance away from tens of millions of Americans — and galvanized by a progressive “resistance” that has yanked the party to the left since Donald Trump was elected president — an increasing number of Democratic elected officials are coalescing around a new health care message in the run-up to the 2018 midterm elections: It’s time for single-payer insurance.

The shift has been dramatic. A majority of voters (53 percent) now back the idea of all Americans receiving coverage through a single government plan, up from 40 percent in 1998-2000, according to a recent Kaiser Family Foundation poll. In the House, Rep. John Conyers Jr.’s “Medicare for All” bill has already attracted 113 co-sponsors — nearly twice as many as in the last congressional session, and more than half of the entire Democratic caucus. Sen. Elizabeth Warren is urging Democrats to run on single-payer in 2018 and 2020, and Sen. Bernie Sanders, whose insurgent bid for the party’s presidential nomination thrust the issue into the national spotlight, is set to introduce his own single-payer plan after the Obamacare debate concludes.

Senate Majority Leader Mitch McConnell, R-Ky., leaves the Senate chamber after announcing the revised version of the Republican health care bill. The bill has been in jeopardy because of opposition within the GOP ranks. (Photo: J. Scott Applewhite/AP)

“Where we should be going is to join the rest of the industrialized world and guarantee health care to all people as a right,” Sanders said in March.

But could campaigning under the banner of government-run health insurance really propel Democrats back to power in Washington, D.C.? And if so, could they really transform America into a single-payer country like Canada?

For a preview of the road ahead — and the potential pitfalls — there’s no better place to look than California.

The Golden State has been on the front lines of the single-payer fight for decades now. In Sacramento, Democrats have introduced at least seven single-payer bills since 1992. Two of them passed the legislature — one in 2006 and one in 2008. Both were vetoed by then-Gov. Arnold Schwarzenegger, a Republican. “Socialized medicine is not the solution to our state’s health care problems,” Schwarzenegger said at the time, invoking his predecessor Ronald Reagan.

This time, however, was supposed to be different. In 2011, Democrat Jerry Brown, who argued for a single-payer system during his 1992 presidential campaign, succeeded Schwarzenegger as governor. Five years later, Democrats won supermajorities in both houses of the California legislature. And earlier this year, two state senators introduced another bill (SB 562) designed to wipe out California’s private insurance market and create a single-payer system.

The old barriers had finally broken down. The stars were aligned. And yet, after SB 562 passed the more progressive state Senate, Assembly Speaker Anthony Rendon (who insists he supports single-payer) abruptly intervened in late June and shelved the bill for the remainder of the 2017 session.

California Gov. Jerry Brown speaks during an event on health care at the U.S. Capitol March 22, 2017. (Photo: Alex Wong/Getty Images)

“SB 562 was sent to the Assembly woefully incomplete,” Rendon snapped. “Even senators who voted for SB 562 noted there are potentially fatal flaws in the bill, including the fact it does not address many serious issues, such as financing, delivery of care, cost controls, or the realities of needed action by the Trump Administration and voters to make SB 562 a genuine piece of legislation.”

Gov. Brown, meanwhile, piled on.

“Where do you get the extra money?” Brown told reporters. “You take a problem and say I’m going to solve it by something that’s even a bigger problem, which makes no sense.”

Progressive activists were furious. Rendon and his family received death threats. Outside the speaker’s Capitol office, one protester pretended to stab a bear in the back with a fake knife; the blade had “Rendon” written on it. With public opinion turning, Republicans floundering in Washington, and Democrats firmly in control of both the governor’s mansion and the legislature, activists wondered why squander a perfect opportunity to make the left’s single-payer dream a reality? Why chicken out now?

It’s an important question — and a revealing one for progressives who hope that single-payer will finally go national in the wake of the GOP’s war against Obamacare.

Among single-payer proponents here in California, two competing explanations for SB 562’s implosion have emerged. If you agree with Rendon’s decision, you’re likely to believe that the bill itself, and the activists behind it, are to blame. And if you disagree with Rendon’s decision, you probably think cash is the real culprit.

Both rationales should trouble Democrats who want their party to run on — and eventually implement — a nationwide single-payer system.

Yolanda Sanchez, left, and her daughter, Michele Sanches-Nelson, a registered nurse, wait in line with other members of the California Nurses Association and supporters to enter the Capitol to call for a single-payer health plan, Wednesday, June 28, 2017, in Sacramento, Calif. (Photo: Rich Pedroncelli/AP)

The “blame the bill” explanation is complicated, having to do in part with the peculiarities of California’s legislative process, which is constrained in complex ways by ballot initiatives such as one requiring that a set percentage of the budget be devoted to education. But the basic gist is that SB 562 was a mere “shell” of a bill that failed to address many of the major challenges facing such a massive insurance overhaul — see Rendon, above — and that this was a strategic misstep by its major union backer, the California Nurses Association.

“Last decade’s single payer bill … included measures for cost control, patient advocacy, regional planning, quality of care, global budgeting, delivery system improvements, build-out of service networks, incentive payments to recruit health personnel, transition costs, statewide databasing, dispute resolution, fraud prevention, a formulary for prescription drugs, and a lot more,” writes the Intercept’s David Dayen. “It was a serious bill that set real guidelines. … It thought of almost everything. SB 562 kicks nearly all of these questions” down the road.

As a result, Democrats disinclined to shoulder the political risks of transforming California’s entire health insurance system — such as the state’s most powerful Democrat, Gov. Brown — could easily dismiss SB 562 as an unfunded, underbaked pipe dream (even though studies have suggested it would be financially viable.)

The “blame the money” explanation is a lot easier to understand. As Lydia O’Neal and David Sirota report in International Business Times, “Health insurers and pharmaceutical companies [have] substantially boosted their donations to California Democratic candidates in gubernatorial election years,” giving “more than $16 million to Democratic candidates and the California Democratic Party in the 2014 election cycle — almost double what donors from those industries gave in the 2006 election” — and collectively donating more than $3 million to Brown and Rendon since 2010. In short, opponents of Rendon’s decision are claiming that corporations have bought him (and other like-minded Democrats) off.

So why should both of these competing explanations unsettle national single-payer proponents?

Because both of them vividly illustrate how much intraparty resistance single-payer would generate even if Democrats were to win back Congress in 2018 and the presidency in 2020 (which is a big if). National Democrats — especially those from swing districts — are even more risk-averse than their counterparts in deep-blue California, and many of them would be similarly inclined to avoid voting on a measure that opponents could caricature as a budget-busting foray into “socialized medicine.” National Democrats also receive a lot of money from the health industry — $69 million in 2016 alone. If Democrats can’t pass single-payer in Sacramento, there’s little chance they could pass it in Washington, D.C.

Not that this will prevent more and more Dems from running on single-payer in the coming elections. After all, that’s what Democrats have been doing in California for decades now. In fact, if the party does win back Congress in 2018, legislators may even send a single-payer bill to Donald Trump’s desk, just as California Democrats did with Schwarzenegger. What the state’s latest single-payer skirmish shows, however, is that the calculus changes when it’s a Democrat who would have to sign such a bill into law. Single-payer proponents might dream of what’s possible under a unified Democratic government. But so far, at least, California has provided a disappointing answer: not much.